METHOD FOR PREPARING LIQUID FUEL BY USING y- VALEROLACTONE

ABSTRACT

The present invention provides a method for preparing liquid fuel by using γ-valerolactone, and steps are as follows: placing a phosphoric acid solution and γ-valerolactone in a reaction tank for reaction at 220-260° C. for 3-12 hours, cooling to room temperature to obtain a liquid fuel. Using the phosphoric acid solution as a catalyst, γ-valerolactone can be catalytically converted in one step at a mild temperature (220-260° C.) to produce light and heavy oil products with high calorific value, with a total oil yield up to 33.5 wt %. This technique is simple in process flow and convenience to operate, and has industrial application prospects. Compared with other technologies for preparing high-grade oil products by catalytically converting γ-valerolactone, using the phosphoric acid solution for catalytic conversion has the obvious advantages that no expensive hydrogen needs to be provided externally, the reaction process is simple, and the temperature is mild.

TECHNICAL HELD

The present invention relates to the technical field of preparation of renewable liquid fuel, and particularly, relates to a method for preparing a high-grade liquid fuel by catalytic conversion of γ-valerolactone by using a phosphoric acid solution.

BACKGROUND

With the depletion of petrochemical resources, the development and utilization of renewable biomass liquid fuel is an important means to solve the energy crisis. γ-valerolactone is an important bio-based platform compound, which can obtained by acid hydrolysis of cellulose in plants to produce levulinic acid followed by hydrogenation reaction of levulinic acid and self-esterification. However, γ-valcrolactone has high water solubility and low calorific value, which greatly limits its application as a high-grade fuel for vehicles. A possible method of using γ-valerolactone is to convert it into a hydrocarbon-based liquid fuel of moderate molecular weight, which can be used to replace petrochemical gasoline (mainly C4-C12) or diesel (C10-C22). Since γ-valerolactone is a low molecular compound (C5H₈O₂) containing an ester bond, its conversion into a high-grade liquid fuel requires multi-step reaction, including hydrodeoxygenation and acid-catalyzed oligomerization, etc. In general, hydrodeoxygenation of γ-valerolactone requires higher reaction temperature (e.g. 300° C.) and higher pressure (e.g. 35 MPa) conditions. The high price of hydrogen in the hydrogenation process is an important factor limiting the preparation of the high-grade liquid fuel by γ-valerolactone. In addition, the multi-step reaction required during the conversion of γ-valerolactone and the higher temperature also cause high process costs. Therefore, the development of a new type of catalytic reaction system, in the absence of hydrogenation and under a condition of mild temperature, one-step conversion of γ-valerolactone into high-grade liquid fuel is of great importance.

SUMMARY OF THE INVENTION

The present invention provides a method of converting γ-valerolactone in one step into a high-grade liquid fuel under a mild condition using 100% phosphoric acid solution as a catalyst, which solves the multi-step reaction process and harsh reaction conditions (such as high temperature, catalytic hydrogenation, etc.) required for the preparation of the high-grade liquid fuel by using γ-valerolactone.

The present invention is achieved by the technical solution as follows: a method for preparing liquid fuel by using γ-valerolactone comprises steps as follows: placing phosphoric acid solution and γ-valerolactone in a reaction tank for reaction at 220-260° C. for 3-12 hours, cooling to room temperature to obtain a liquid fuel.

Said phosphoric acid solution has a mass concentration of 100%.

A mass ratio of γ-valerolactone to the phosphoric acid solution is 1:(2-100).

The phosphoric acid solution and γ-valerolactone are placed in the reaction tank, and heated up to 220-260° C. at 5-10° C./min.

Preferably, a method for preparing liquid fuel by using γ-valerolactone comprises steps as follows:

(1) placing γ-valerolactone and a phosphoric acid solution in reaction tank for reaction at 220-260° C. for 3-12 hours, after complete reaction, cooling to room temperature to obtain a liquid fuel;

(2) performing rotary evaporation on the liquid fuel cooled in the step (1) to obtain an oil-water mixture and a phosphoric acid mixture, performing oil-water separation on the oil-water mixture to obtain light oil, and the rotary evaporation is performed at 240° C., under a pressure of −0.09 MPa; and

(3) performing extraction on the phosphoric acid mixture obtained in the step (2) with dichloromethane, distilling a dichloromethane solution obtained after the extraction by a rotary evaporator to obtain dichloromethane and heavy oil, and rotary evaporation is performed at a temperature of 60° C., under a pressure of −0.09 MPa.

The light oil has a boiling point ≤240° C., and the heavy oil has a boiling point ≥240° C.

Temperature and pressure critical conditions for the separation of the obtained light oil and the heavy oil are 240° C. and −0.09 MPa. Based on the correspondence between the boiling point and the pressure, under normal pressure, the boiling point of the light oil is ≤245° C. and the boiling point of the heavy oil is ≥245° C.

The main reaction pathway for the conversion of γ-valerolactone into liquid fuel is shown in the figure below. In an acidic solution, the conversion of γ-valerolactone into 4-hydroxyvaleric acid is a reversible reaction, and meanwhile 4-hydroxyvaleric acid can be dehydrated to form 3-pentenoic acid under a condition of heating and acid catalysis. Using 100% phosphoric acid as a catalyst and γ-valerolactone and 3-pentenoic acid as reaction materials, it was found that products of both were completely identical, which proved that 3-pentenoic acid was an important intermediate product of the conversion of γ-valerolactone into liquid fuel. After the reaction, CO₂ and 2-butene were detected in a gas product by headspace gas chromatography-mass spectrometry analysis, indicating that decarboxylic reaction of 3-pentenoic acid occurred; at the same time, CO₂, water and some unsaturated ketone compounds produced during the reaction indicated that ketonization reaction of 3-penteoic acid occurred during the reaction. Under the condition of phosphoric acid catalysis, aromatic cyclization reaction, alkylation reaction, oligomerization reaction, etc., further occurred between the unsaturated ketone compounds and between the unsaturated ketone compounds and 2-butene to generate aromatic compounds and cycloalkane compounds.

The main reaction pathway for the conversion of γ-valerolactone into hydrocarbon compounds

The beneficial effects of the present invention are as follows:

(1) using the phosphoric acid solution as a catalyst, γ-valerolactone can be catalytically converted in one step at a mild temperature (220-260° C.) to produce light and heavy oil products with high calorific value, with a total oil yield up to 31 wt %, and this technique is simple in process flow and convenience to operate, and has industrial application prospects;

(2) the light oil has C and H mass fractions of 88.0% and 8.9%, respectively, and calorific value up to 42.4 MJ/kg; the heavy oil product has C and H mass fractions as high as 85.7% and 9.5%, respectively, and calorific value as high as 41.6 MJ/kg; the calorific values of the light oil and the heavy oil are comparable to the calorific value of commercial oxygenated gasoline (see Table 1);

(3) under the condition of phosphoric acid catalysis, part of the oxygen in γ-valerolactone is removed in form of carbon dioxide, and the decarboxylation rate is 49%; and

(4) catalytic conversion of γ-valerolactone by the phosphoric acid solution has obvious advantages of requiring no external hydrogen supply which is expensive, simple reaction process (one-step reaction), mild temperature (temperature below 260° C.) compared to other techniques for catalytically converting γ-valerolactone to produce high-grade oil product.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a process flow chart for the present invention.

FIG. 2 is a gas chromatography-mass spectrometry analysis product for light oil in Example 1.

FIG. 3 is infrared spectra of light oil and heavy oil in Example 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Example 1

The specific steps of the present example using phosphoric acid to convert poly-3-hydroxybutyrate to prepare liquid fuel are as follows (see FIG. 1 for the flow chart):

(1) 15 g of γ-valerolactone and 60 mL of a phosphoric acid solution (112.2 g) were taken and placed in a 100 mL para-polyphenyl reaction tank. The temperature was programmed to rise to 240° C. at 5° C./min, and maintained at a constant temperature of 240° C. for 6 hours. After the reaction, it was rapidly cooled to room temperature with cold water. It was found by high-performance liquid chromatography that γ-valerolactone was completely converted basically, 49% of the oxygen in γ-valerolactane was removed in form of carbon dioxide, and some oxygen was removed in form of water and carbon monoxide;

(2) rotary evaporation was performed on the product after the reaction of the step (1) at a condition of 240° C. and −0.09 Mpa to obtain an oil-water mixture and a phosphoric acid mixture, and the oil-water mixture was separated by a separating funnel to obtain light oil with a yield of 24.8 wt %; and

(3) extraction was perforated on the evaporated phosphoric acid mixture obtained in the step (2) with dichloromethane, and the extracted dichloromethane solution was subjected to rotary distillation under a condition of 60° C. and −0.09 Mpa to recover dichloromethane and to obtain heavy oil with a yield of 8.7%.

Yields, C, H element distribution and calorific values of the hydrogen oil and heavy oil Obtained in the present example are shown in Table 1.

TABLE 1 Yields, C, H element distribution and calorific values of light oil and heavy oil Element distribution Calorific value Yield (wt %) C (wt %) H (wt %) (MJ/kg) Light oil 24.8 88.0 8.9 42.4 Heavy oil 8.7 85.7 9.5 41.6 Commercial 80.4 12.3 41.8 oxygenated gasoline

FIG. 2 is molecular structural formulas of main products identified by gas chromatography-mass spectrometry analysis of the prepared light oil product. As can be seen from FIG. 2, the main products are a low molecular unsaturated benzene ring compounds and cycloalkane compounds.

These main products shown in FIG. 2 were further verified by infrared spectroscopy analysis of the light oil product in FIG. 3. It can be seen from FIG. 3 that the light oil product contains a C—H vibration peak (2800-3100 cm⁻¹) including methyl, methylene and methine, and an aromatic ring functional group (1600 cm ⁻¹, 1460 cm⁻¹); and there is no obvious vibration peak at 3200-3670 cm ⁻¹, indicating that there are almost no hydroxyl and carboxyl functional groups in the oil product, and γ-valerolactone is successfully decarboxylated. There is a small vibrational peak at 1780 cm⁻¹, indicating that the oil product contains a small amount of ketone compound, which is consistent with the result of the GCMS analysis in FIG. 2. In addition, the infrared spectrum of the heavy oil is basically similar to that of the light oil, indicating that the main components in the heavy oil also include C—H functional groups including methyl, methylene and methine, and aromatic functional groups.

Example 2

15 g of γ-valerolactone and 15 mL of a phosphoric acid solution (28 g) were taken and placed in a 100 mL para-polyphenyl reaction tank. The temperature was programmed to rise to 260° C. and maintained at a constant temperature of 260° C. for 6 hours. After the reaction, it was cooled to room temperature. Light oil was obtained by rotary evaporation, and heavy oil was obtained by extraction using dichloromethane and distillation.

Example 3

1 g of γ-valerolactone and 50 mL of a phosphoric acid solution (93.7 g) were taken and placed in a 100 mL para-polyphenyl reaction tank. The temperature was programmed to rise to 220° C. at 8° C./min and maintained at a constant temperature of 220° C. for 12 hours. After the reaction, it was cooled to room temperature. Light oil was obtained by rotary evaporation, and heavy oil was obtained by extraction using dichloromethane and distillation.

Example 4

10 g of γ-valerolactone and 60 mL of a phosphoric acid solution were taken and placed in a para-polyphenyl reaction tank. The temperature was programmed to rise to 250° C. at 10° C./min and maintained at a constant temperature of 250° C. for 3 hours. After the reaction, it was cooled to room temperature. Light oil was obtained by rotary evaporation, and heavy oil was obtained by extraction using dichloromethane and distillation.

Example 5

1 g of γ-valerolactone and 1.07 mL of a phosphoric acid solution with a mass concentration of 100% (2 g) were placed in a 20 mL para-polyphenyl reaction tank. The temperature was programmed to rise to 260° C. at 10° C./min and was maintained for 5 hours. After the reaction, it was cooled to room temperature. Light oil was obtained by rotary evaporation, and heavy oil was obtained by extraction using dichloromethane and distillation.

Example 6

1 g of γ-valerolactone and 53.4 mL of a phosphoric acid solution with a mass concentration of 100% (100 g) were placed in a para-polyphenyl reaction tank. The temperature was programmed to rise to 230° C. at 5° C./min and was maintained for 8 hours. After the reaction, it was cooled to room temperature. Light oil was obtained by rotary evaporation, and heavy oil was obtained by extraction using dichloromethane and distillation.

Example 7

1 g of γ-valerolactone and 26.7 mL of a phosphoric acid solution with a mass concentration of 100% (50 g) were placed in a para-polyphenyl reaction tank. The temperature was programmed to rise to 260° C. at 10° C./min and maintained for 5 hours. After the reaction, it was cooled to room temperature. Light oil was obtained by rotary evaporation, and heavy oil was obtained by extraction using dichloromethane and distillation. 

1. A method for preparing liquid fuel by using γ-valerolactone, characterized in that, the method comprises steps as follows: placing a phosphoric acid solution and γ-valerolactone in a reaction tank for reaction at 220-260° C. for 3-12 hours, cooling to room temperature to obtain a liquid fuel.
 2. The method for preparing liquid fuel by using γ-valerolactone according to claim 1, wherein the phosphoric acid solution has a mass concentration of 100%.
 3. The method for preparing liquid fuel by using γ-valerolactone according to claim 1, wherein a mass ratio of γ-valerolactone to the phosphoric acid solution is 1:(2-100).
 4. The method for preparing liquid fuel by using γ-valerolactone according to claim 1, wherein placing the phosphoric acid solution and γ-valerolactone in the reaction tank and heating up to 220-260° C. at 5-10° C./min.
 5. A method for preparing liquid fuel by using γ-valerolactone according to claim 1, wherein the method comprises steps as follows: placing γ-valerolactone and the phosphoric acid solution in the reaction tank for reaction at 220-260° C. for 3-12 hours, after complete reaction, cooling to room temperature to obtain the liquid fuel; preforming rotary evaporation on the liquid fuel cooled in the step (1) to obtain an oil-water mixture and a phosphoric acid mixture, performing oil-water separation on the oil-water mixture to obtain light oil, and the rotary evaporation is performed at a temperature of 240° C., under a pressure of −0.09 MPa; and performing extraction on the phosphoric acid mixture obtained in the step (2) with dichloromethane, distilling a dichloromethane solution obtained after the extraction by a rotary evaporator to obtain dichloromethane and heavy oil, and the rotary evaporator is operated at a temperature of 60° C., under a pressure of −0.09 MPa.
 6. The method for preparing liquid fuel by using γ-valerolactone according to claim 5, wherein the method comprises a step that at normal pressure, the light oil has a boiling point ≤245° C., and the heavy oil has a boiling point ≥245° C.
 7. A method for preparing liquid fuel by using γ-valerolactone according to claim 2, wherein the method comprises steps as follows: placing γ-valerolactone and the phosphoric acid solution in the reaction tank for reaction at 220-260° C. for 3-12 hours, after complete reaction, cooling to room temperature to obtain the liquid fuel; preforming rotary evaporation on the liquid fuel cooled in the step (1) to obtain an oil-water mixture and a phosphoric acid mixture, performing oil-water separation on the oil-water mixture to obtain light oil, and the rotary evaporation is performed at a temperature of 240° C., under a pressure of −0.09 MPa; and performing extraction on the phosphoric acid mixture obtained in the step (2) with dichloromethane, distilling a dichloromethane solution obtained after the extraction by a rotary evaporator to obtain dichloromethane and heavy oil, and the rotary evaporator is operated at a temperature of 60° C., under a pressure of −0.09 MPa.
 8. The method for preparing liquid fuel by using γ-valerolactone according to claim 7, wherein the method comprises a step that at normal pressure, the light oil has a boiling point ≤245° C., and the heavy oil has a boiling point ≥245° C.
 9. A method for preparing liquid fuel by using γ-valerolactone according to claim 3, wherein the method comprises steps as follows: placing γ-valerolactone and the phosphoric acid solution in the reaction tank for reaction at 220-260° C. for 3-12 hours, after complete reaction, cooling to room temperature to obtain the liquid fuel; preforming rotary evaporation on the liquid fuel cooled in the step (1) to obtain an oil-water mixture and a phosphoric acid mixture, performing oil-water separation on the oil-water mixture to obtain light oil, and the rotary evaporation is performed at a temperature of 240° C., under a pressure of −0.09 MPa; and performing extraction on the phosphoric acid mixture obtained in the step (2) with dichloromethane, distilling a dichloromethane solution obtained after the extraction by a rotary evaporator to obtain dichloromethane and heavy oil, and the rotary evaporator is operated at a temperature of 60° C., under a pressure of −0.09 MPa.
 10. The method for preparing liquid fuel by using γ-valerolactone according to claim 9, wherein the method comprises a step that at normal pressure, the light oil has a boiling point ≤245° C., and the heavy oil has a boiling point ≥245° C.
 11. A method for preparing liquid fuel by using γ-valerolactone according to claim 4, wherein the method comprises steps as follows: placing γ-valerolactone and the phosphoric acid solution in the reaction tank for reaction at 220-260° C. for 3-12 hours, after complete reaction, cooling to room temperature to obtain the liquid fuel; preforming rotary evaporation on the liquid fuel cooled in the step (1) to obtain an oil-water mixture and a phosphoric acid mixture, performing oil-water separation on the oil-water mixture to obtain light oil, and the rotary evaporation is performed at a temperature of 240° C., under a pressure of −0.09 MPa; and performing extraction on the phosphoric acid mixture obtained in the step (2) with dichloromethane, distilling a dichloromethane solution obtained after the extraction by a rotary evaporator to obtain dichloromethane and heavy oil, and the rotary evaporator is operated at a temperature of 60° C., under a pressure of −0.09 MPa.
 12. The method for preparing liquid fuel by using γ-valerolactone according to claim 11, wherein the method comprises a step that at normal pressure, the light oil has a boiling point ≤245° C., and the heavy oil has a boiling point ≥245° C. 